This invention relates to an ion beam working apparatus for carrying out fine working of a sample surface using focused ion beam irradiation.
Conventionally, as is in Japanese Patent Publication No. H.3-163741, it was a working method wherein an optimum aperture diameter corresponding to the size of a working area of working using focused ion beam irradiation is stored in a computer and working conditions are selected and set from those stored conditions and working is carried out.
With this apparatus working of a sample surface is carried out in the following way, by means of radiation of a focused ion beam onto the sample surface image observation of the sample surface is carried out, on the basis of this image observation a focused ion beam irradiation area (scanning area) is set, and the focused ion beam is scan-radiated in the irradiation area. At the sample surface irradiated with the focused ion beam, by ion sputtering, the surface of the focused ion beam irradiation area (the scanned area) is removed. Also, if simultaneously with the focused ion beam radiation an organic compound vapor is blown against that area, organic compound adsorbed onto the sample surface is decomposed by the ion beam irradiation and a solid thin film is formed on that area.
Also, if instead of an organic compound vapor a vapor of a substance having an etching action with respect to the substance constituting the sample is blown against it, the substance constituting the sample and that vapor are caused by the focused ion beam irradiation to react and faster etching removal working can be carried out.
With a conventional method, the ion beam current is selected according to the size of the working area, and throughput is thereby increased, but when the ion beam current is changed a shift in the focal point and a shift in the image occur. Because of this, it was not possible to carry out continuous working of a plurality of workings with good accuracy automatically. In particular, the focused ion beam is radiated onto the sample surface with predetermined focused ion beam irradiation conditions, the sample surface is observed and on the basis of that sample observation image the focused ion beam irradiation area (working area) is set. After that, the focused ion beam radiation conditions (the opening diameter of the electric variable multi-aperture) are changed and the focused ion beam is scan-radiated onto the irradiation area again and the sample surface is worked. When the opening diameter of the electric variable multi-aperture is changed, the ion beam current of the focused ion beam changes, and the irradiation locus of the focused ion beam also shifts. Therefore, when the sample surface is worked using focused ion beam irradiation in the observed image, the worked area differs from the target area and correct working cannot be performed. To eliminate this shift, it is necessary to scan-radiate the focused ion beam and carry out image observation and set the working area again with the changed opening diameter of the electric variable multi-aperture.